Reduction of Cu(II) in matrix-assisted laser desorption/ionization mass spectrometry

Zhang, Juan; Frankevich, Vladimir; Knochenmuss, Richard; Friess, Sebastian D.; Zenobi, Renato

doi:10.1016/s1044-0305(02)00807-3

Cited by 68 publications

(77 citation statements)

References 41 publications

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“…In the ion source, gas-phase reactions, such as redox reactions, may occur between the electronically excited analyte ions and matrix ions/molecules. For example, the mechanism of the reduction of Cu (II) to Cu (I) in MALDI was studied, and it was found that this reduction was caused by gas-phase charge exchange with matrix molecules, which is a thermodynamically favorable process [15]. Recently, studies of a MALDI insource photo-oxidation reaction have shown that on a photoelectrode-modified target plate, hydroquinone can be photo-oxidized to benzoquinone by UV laser excitation [16].…”

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confidence: 99%

Gas-phase scrambling of disulfide bonds during matrix-assisted laser desorption/ionization mass spectrometry analysis

Zhao¹,

Almaraz

Fan

et al. 2009

J. Am. Soc. Mass Spectrom.

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Evidence for photo-induced radical disulfide bond scrambling in the gas phase during matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) is described. The phenomenon was observed during the analysis of tryptic peptides from insulin and was confirmed in the determination of disulfide bonds in the rhamnose-binding lectin SEL24K from the Chinook salmon Oncorhynchus tshawytscha. A possible mechanism for this surprising scrambling is proposed. Despite this finding, the disulfide bond pattern in SEL24K was assigned unambiguously by a multi-enzyme digestion strategy in combination with MALDI mass spectrometry. The pattern was found to be symmetrical in the tandem repeat sequence of SEL24K. To the best of our knowledge, this is the first report of disulfide bond scrambling in the gas phase during MALDI-MS analysis. This observation has important ramifications for unambiguous assignment of disulfide bonds. (J Am Soc

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mentioning

confidence: 99%

Gas-phase scrambling of disulfide bonds during matrix-assisted laser desorption/ionization mass spectrometry analysis

Zhao¹,

Almaraz

Fan

et al. 2009

J. Am. Soc. Mass Spectrom.

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“…The latter processes may be responsible for oxygen release, effectively stabilizing the resulting species. The occurrence of these mechanisms has been recently demonstrated for copper chlorides and small peptides deposited on different conductive and isolating surfaces [63][64][65]. Moreover, these electrons may also ionize neutrals species if their kinetic energy is high enough [21].…”

Section: Study Of Cluster Ion Formation By La-msmentioning

confidence: 97%

Laser ablation mass spectrometry of inorganic transition metal compounds. Additional knowledge for the understanding of ion formation

Aubriet

Müller

2008

J. Am. Soc. Mass Spectrom.

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Laser ablation of transition-metal oxides have been investigated to better understand the formation processes of inorganic cluster ions. The study of binary oxide mixtures and the relative distribution of the ions produced suggest three salient mechanisms that occur after laser/matter interaction, that function to produce the observed ensemble of ionic species. Molecular recombination reactions, unimolecular dissociation processes, emission of small neutrals, including molecular oxygen from transition-metal oxide samples, or from species expelled in gas phase appear to be a significant mechanism, especially under high laser irradiance conditions. These processes are used to propose a set of pathways to rationalize the envelope of ionic clusters formed under photon bombardment. T he study of ion formation processes by mass spectrometry during inorganic compound laser ablation is not yet fully understood. However, several models have been proposed to describe and explain the laser ablation of inorganic compounds [1][2][3][4][5][6][7]. The interaction of a laser beam with a non-metallic solid induces different processes, leading to ejection of neutral and ionized species into the gas phase. Haglund proposed a qualitative description of these processes [7], which begins with the assumption that laser sputtering could be decomposed into four phases: (1) the absorption of laser energy by one or multiple-photon processes; (2) the conversion of the incident energy through radiative and non-radiative relaxation processes; (3) the ejection of species-atoms, molecules, neutrals, ions, excited species-from the irradiated surface; and (4) the formation and the expansion of a more or less dense plume of neutrals and ions. Two lasermatter interaction regimes have to be considered: the laser desorption (LD) and the laser ablation (LA). It is generally reported that LD results in emission of ions, atoms, and molecules without any substantial disturbance in the surrounding surface. LA implies a largescale disruption of surface and near-surface geometrical and electronic structure. These substantial qualitative differences allowed Haglung to identify desorption with a microscopic, and ablation with a mesoscopic view point. LD and LA have to be viewed as the extremes of a continuum, which ranges from the emission of isolated neutrals or ions in the case of LD to the massive removal of material resulting from the collective effects of multiple photons irradiating the same spatial locale in the case of LA. The phenomenology of LA is thought of in terms of formation of a plume of ejected species, which follows the laws of plasma and gas dynamics, and produces a large number of ionized species. Collisions of ions with neutrals occurring in the gas-phase plume after LA lead to ion-molecule condensation reactions. On the other hand, ions and neutrals possess a significant amount of energy, which can result in dissociation reactions. The length scale associated with laser ablation is on the order of d Х laser ϫv s , where laser is the dur...

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“…34 Furthermore, Cu(II) ion reduction was inversely proportional to the concentration of the analytes, and thus the thickness of the deposited analyte would affect the reduction, as in the case of MALDI. 16,25 These findings suggest that electron transfer from the sample target to analytes is likely in DIOS as well, although the ionization mechanism of DIOS is unknown.Juhasz and Costello reported on the oxidation of oligomers and polymers containing ferrocene and ruthenocene moieties in MALDI measurements. 37 They described that either electron transfer from the analyte to the chemical matrix or direct photoionization of the analayte could account for their results.…”

mentioning

confidence: 99%

mentioning

confidence: 99%

“…[1][2][3][4][5][6] While the mechanism of ionization is largely unknown, physical data on the ionization potentials and the gas-phase acidity or basicity have been accumulating, and the roles of the matrix-matrix, matrix-analyte and analyte-analyte reactions in both primary and secondary ionization events have been evaluated in some detail. [7][8][9][10][11][12][13][14][15][16] These studies have suggested the secondary ionmolecule reactions in the plume to be essential to understanding the process of ionization and the mass spectrum. 7,9,11 Some analytes are reduced by these reactions as follows: Copper(II) ions are reduced by laser desorption/ionization (LDI) with or without a chemical matrix.…”

mentioning

confidence: 99%

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Oxidation of Ferrocene Derivatives in Desorption/Ionization on Porous Silicon

2005

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Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) is currently an indispensable method for analyzing biomolecules and synthetic polymers. [1][2][3][4][5][6] While the mechanism of ionization is largely unknown, physical data on the ionization potentials and the gas-phase acidity or basicity have been accumulating, and the roles of the matrix-matrix, matrix-analyte and analyte-analyte reactions in both primary and secondary ionization events have been evaluated in some detail. [7][8][9][10][11][12][13][14][15][16] These studies have suggested the secondary ionmolecule reactions in the plume to be essential to understanding the process of ionization and the mass spectrum. 7,9,11 Some analytes are reduced by these reactions as follows: Copper(II) ions are reduced by laser desorption/ionization (LDI) with or without a chemical matrix. 16Flavin-containing compounds, such as riboflavin, riboflavin 5′-phosphate and flavin-adenine dinucleotide, are reduced in MALDI and fast atom bombardment (FAB) ionization, but not in electrospray ionization, as reported by Itoh et al., who also found that the reduction levels depend on the matrix molecule types. 17 In the case of nitrotyrosine, the NO2 moiety is partially converted into NH2, probably due to reduction after photo-induced dissociation by UV laser irradiation. 18,19 Similarly, the S-nitrosylated cysteine, Cys(SNO), in peptides is completely converted to cysteine, Cys(SH), in MALDI. 20,21 Different mechanisms, such as electron capture and charge exchange with the chemical matrix, have been proposed to account for the reductions in MALDI. 8,9 A line of studies has indicated that free electrons are formed by photoelectric emission from the metal/dielectric-substance interface. [22][23][24][25] The metal sample target is not the photoelectron source, because the work function of metals is greater than the photon energy. 23 The presence of matrix molecules or analytes placed on a metal target enhances electron emission via band bending and the associated reduction in work function. 22,23 Thus, electron transfer from the sample target would be essential for understanding the analyte reduction in LDI.In desorption/ionization on porous silicon, termed DIOS, 26 analytes are deposited on a silicon chip, which is prepared by electrochemical anodization or chemical etching of crystalline silicon, for LDI without the addition of a chemical matrix. The DIOS mass spectra are thus free of cluster ions of the matrix, facilitating identification of the ions of small analyte molecules. DIOS-MS has been applied to various kinds of compounds, such as peptides, natural products, small organic molecules and synthetic polymers. [26][27][28][29][30][31][32][33][34][35][36] The ionization efficiency of DIOS relies on a porous scaffold providing a sufficient surface area to retain analytes, and on the UV-absorptive property, which affords the transfer of laser energy to analytes. 26,27 In contrast to MALDI, chemical reactions in a plume composed of analytes and the sample ma...

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Reduction of Cu(II) in matrix-assisted laser desorption/ionization mass spectrometry

Cited by 68 publications

References 41 publications

Gas-phase scrambling of disulfide bonds during matrix-assisted laser desorption/ionization mass spectrometry analysis

Gas-phase scrambling of disulfide bonds during matrix-assisted laser desorption/ionization mass spectrometry analysis

Laser ablation mass spectrometry of inorganic transition metal compounds. Additional knowledge for the understanding of ion formation

Oxidation of Ferrocene Derivatives in Desorption/Ionization on Porous Silicon

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